Bucharest, Romania (CNN) -- Employees of the Romanian Work and Health Ministries and the Romanian Mail joined a protest by Finance Ministry employees Thursday, and unions said teachers and policemen may also join the action.

Some 200 finance ministry employees spontaneously began their protest Wednesday at noon, angry about wage cuts. They spent the night in the building's hallways and were still there Thursday, union leaders said.

The workers vowed not to stop protesting until they get their wage incentives back, union leaders said. They stopped work in the headquarters and branch offices across the country.

Finance Minister Gheorghe Ialomitianu, who returned to his office Wednesday evening after a government meeting, couldn't leave until late at night because protesters booed him every time he tried to get out of the office.

Ialomitianu eventually got out of the building with help of security forces, but protesters threw papers at him as he left.

The finance minister calls the protests illegal and says those who aren't at work won't be paid for the days they're off the job. He needed protection when he went to the ministry Thursday.

All work ministry employees in the capital, Bucharest, and around the country joined the finance ministry protests, said Ingrid Moldoveanu, general secretary of the National Public Employees Union.

They are protesting in front of their buildings across the country, angry about the revocation of wage incentives, Moldoveanu said.

The wage incentives had made up as much as 60 percent of the employees' total income before they were taken away in July. The incentive money had been a redistribution of funds that came from outside the government's budget, for example from uncovering tax evasion cases.

At the same time the incentives were revoked, the government cut public-sector salaries by 25 percent as an austerity measure.

Former Finance Minister Sebastian Vladescu was fired because he insisted on keeping the financial supplements for the ministry's employees.

The protest comes at a difficult time for the finance ministry, which is working on the budget law for next year and is preparing for an evaluation visit by the International Monetary Fund on October 22.